Renal function analysis method and apparatus
A method for measuring a glomerular filtration rate of a mammalian subject comprises a source of reporter and marker fluorescent molecules. The fluorescent molecules are introduced into the vascular system of the mammalian subject. Over a period of time, a measurement of the intensities of the reporter and marker fluorescent molecules is taken. A ratio is calculated to determine the glomerular filtration rate.
1. A system for measuring the fluorescence intensity of a reporter fluorescent molecule and a marker fluorescent molecule in a vascular system of a mammalian subject to determine glomerular filtration rate (GFR) of the kidney of the mammalian subject, the system comprising:
a source of said reporter fluorescent molecule and said marker fluorescent molecule;
a means for introducing said reporter fluorescent molecule and said marker fluorescent molecule into the vascular system of the mammalian subject;
a means for measuring the fluorescence intensity of said reporter fluorescent molecule and said marker fluorescent molecule within the vascular system of the mammalian subject;
a means for determining an intensity ratio of the fluorescence intensity of said measured reporter fluorescent molecule and marker fluorescent molecule within the vascular system of the mammalian subject, and
a means for calculating glomerular filtration rate (GFR) of the mammalian subject according to the equation:
G
F
R
=
V
1
(
A
2
+
B
2
)
A
2
/
α
+
B
2
/
β
wherein V 1 is plasma volume; A 2 and B 2 are constants; α is a fast phase decay constant; and β is a slow phase decay constant;
wherein the ratio of intensity R(t) of the reporter fluorescent molecule and the marker fluorescent molecule are calculated at predetermined intervals; and
wherein the constants A 2 , B 2 , α and β are calculated by fitting the ratio of intensity data to the following equation:
R ( t )= A 2 e αt +B 2 e −βt
where R(t) is the ratio of intensity as a function of time;
wherein said reporter molecule is filtered by the kidney of the mammalian subject, and said marker molecule is retained in the vascular system of the mammalian subject; and
wherein said reporter molecule and said marker molecule are chemically stable in the vascular system during measurement of kidney function.
2. The system of claim 1 wherein said means for introducing includes a catheter.
3. The system of claim 1 wherein said means for measuring includes an optic fiber in communication with a detector.
4. The system of claim 1 wherein said reporter molecule has a first fluorescent characteristic, and said marker molecule has a second fluorescent characteristic, and wherein said first fluorescent characteristic and second fluorescent characteristic are distinguishable.
5. The system of claim 4 wherein the first fluorescent characteristic is a first excitation wavelength and a first emission wavelength and the second fluorescent characteristic is a second excitation wavelength and a second emission wavelength, said first and second fluorescence excitation wavelengths and said first and second fluorescence emission wavelengths being unequal.